Progressive Care Nursing Certification (PCCN) Practice Exam

During an allergic reaction, which mediators are typically released?

1. Insulin

2. Histamine

3. Corticosteroids

4. Prostaglandins

The correct answer is: Histamine

During an allergic reaction, histamine is a key mediator that is typically released by mast cells and basophils. When the immune system identifies a harmless substance as a threat, such as pollen or pet dander, it triggers an inflammatory response. This response involves the degranulation of mast cells, which releases histamine into the surrounding tissues. Histamine plays a crucial role in the allergic response by causing various physiological effects. It increases the permeability of blood vessels, leading to fluid leakage into tissues and causing the classic symptoms of an allergic reaction, such as swelling, redness, and itching. Additionally, histamine stimulates gastric acid secretion and affects respiratory pathways, which can lead to symptoms like bronchoconstriction in cases of asthma. While corticosteroids are anti-inflammatory agents that might be prescribed to manage allergic reactions, they are not released during the reaction itself. Insulin is unrelated to the immune response, and prostaglandins, although involved in inflammation, are not the primary mediators released during an allergic response compared to histamine. Thus, histamine stands out as the primary mediator involved in the acute allergic reaction.